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mm/rmap: skip unfaulted VMAs on anon_vma clone, unlink

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For both anon_vma_clone() and unlink_anon_vmas(), if the source VMA or the
VMA to be linked are unfaulted (e.g.  !vma->anon_vma), then the functions
do nothing.  Simply exit early in these cases.

In the unlink_anon_vmas() case we can also remove a conditional that
checks whether vma->anon_vma is set.

Link: https://lkml.kernel.org/r/085a25f7528e1c8c687276e9b856e88dc8f105ca.1768746221.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Cc: Barry Song <v-songbaohua@oppo.com>
Cc: Chris Li <chriscli@google.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Harry Yoo <harry.yoo@oracle.com>
Cc: Jann Horn <jannh@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Lorenzo Stoakes 2026-01-18 14:50:39 +00:00 committed by Andrew Morton
parent 91901a441f
commit 69e9458455
1 changed files with 13 additions and 9 deletions
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22
mm/rmap.c
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@ -313,6 +313,9 @@ int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
check_anon_vma_clone(dst, src);
if (!src->anon_vma)
return 0;
list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
struct anon_vma *anon_vma;
@ -478,7 +481,10 @@ void unlink_anon_vmas(struct vm_area_struct *vma)
mmap_assert_locked(vma->vm_mm);
/* Unfaulted is a no-op. */
VM_WARN_ON_ONCE(!vma->anon_vma && !list_empty(&vma->anon_vma_chain));
if (!vma->anon_vma) {
VM_WARN_ON_ONCE(!list_empty(&vma->anon_vma_chain));
return;
}
/*
* Unlink each anon_vma chained to the VMA. This list is ordered
@ -502,15 +508,13 @@ void unlink_anon_vmas(struct vm_area_struct *vma)
list_del(&avc->same_vma);
anon_vma_chain_free(avc);
}
if (vma->anon_vma) {
vma->anon_vma->num_active_vmas--;
/*
* vma would still be needed after unlink, and anon_vma will be prepared
* when handle fault.
*/
vma->anon_vma = NULL;
}
vma->anon_vma->num_active_vmas--;
/*
* vma would still be needed after unlink, and anon_vma will be prepared
* when handle fault.
*/
vma->anon_vma = NULL;
unlock_anon_vma_root(root);
/*